I absolutely agree that it's nice for this to exist as an option for users who are used to it. I'm a somewhat heavy emacs user, so I'm not at all opposed to esoteric workflows.
But I think it's clearly proven to be a bad design as a default. Discoverability is very important, especially to people who work a lot with a mouse. And using multiple apps at the same time is a very common work flow, one that an always-on-screen task switcher makes much simpler than an alternate view you have to bring up, especially if that alternate view also obscures all of your windows.
I will also say I find workspaces a hard to use UI, as I always lose context when I have to switch workspace, but maybe this is just how my mind works. And the idea of one-task-per-workspace has never worked well for me, as there are several apps that I use in every task, such as chat or email while I'm coding and while doing a presentation and while writing some design. It also seems to require a lot of setup and discipline.
Finally, as a nitpick, moving apps to a different workspace instead of minimizing to taskbar/systray seems like much more work to me.
Personally I'm a huge fan of Win7's grouped taskbar with window previews, along with its window snap support (extended in Win 10).